Фазовая диаграмма системы Ca-Nd

К оглавлению: Другие диаграммы (Others phase diargams)

Ca-Nd (Calcium-Neodymium) K.A. Gschneidner, Jr. and F.W. Calderwood The assessed phase diagram for the Nd-Ca system is based on the work of [ 71Str1] and [71Str2], with corrections to the melting and transformation temperatures of the end members. [71Str1] reported the melting point of Nd to be 1024 C instead of 1021 C. The melting temperature of Ca was given as 851 C. The accepted value for the melting point of Ca is 842 C. The bCa = aCa transformation temperature on their phase diagram was shown as 464 C, instead of the accepted value of 443 C. Their phase diagram did not explicitly show the bNd = aNd transformation temperature, which occurs at 863 C. Pure Ca occurs in two stable forms. The low-temperature form, aCa, has the fcc structure of the Cu type and is stable below 443 C. Above this temperature, bCa has the bcc structure of the W type. An extensive field of liquid immiscibility, extending from ~23.4 to ~99 at.% Ca, is shown. A monotectic reaction between (bNd) and the melt occurs at 23.4 at.% Nd and 892 C. A eutectic occurs between (bNd) and (bCa) at 99.5 at.% Ca and 831 C. The maximum solid solubility of bCa in (bNd) is 13.4 at.% Ca at the monotectic temperature of 892 C. This solubility decreases to about 12.9 at.% at the eutectic temperature of 831 C. The addition of Ca to Nd decreases the temperature of the b = a transformation in (Nd) from 863 C to the eutectoid temperature of 429 C. On the Ca-rich side of the phase diagram, about 0.1 at.% Nd is in solid solution with Ca at the (bNd)/(bCa) eutectic temperature of 831 C. The addition of a small amount of bNd to aCa raises the b = a transformation temperature from about 443 to 444 C. The maximum amount of bNd soluble in ( aCa) is about 0.14 at.% at 444 C. Because no other work on this system has been reported, the phase diagram remains unverified. The relatively small differences between the reported and accepted melting and transformation temperatures appear to indicate relatively pure starting materials. 71Str1: V.F. Stroganova, V.F. Terekhova, and E.M. Savitskii, in Constitutional Diagrams of Metallic Systems, N.V. Ageev and O.S. Ivanov, Ed., Nauka, Moscow, 186 (1971) in Russian. 71Str2: V.E. Stroganova, V.F. Terekhova, and E.M. Savitskii, in Rare Earth Metals and Alloys, E.M. Savitskii and V.F. Terekhova, Ed., Nauka, Moscow, 51 ( 1971) in Russian. Published in Bull. Alloy Phase Diagrams, 8(6), Dec 1987. Complete evaluation contains 1 figure, 1 table, and 2 references. 1